Vehicles systems receive various operator commands in order to facilitate operator control of the powertrain, including an accelerator pedal position input. Further, the relationship between the amount of pedal depression by the operator and the powertrain response can be tuned to provide different speed and torque controls.
One example approach for adjusting a pedal position map is provided by Weber at al. in U.S. Pat. No. 6,654,677. Therein, a powertrain controller varies the mapping of an accelerator pedal position to an electronic throttle angle based on the vehicle speed to improve operator control over vehicle speed, torque output, and acceleration. In particular, at lower vehicle speeds, the pedal position is mapped to the electronic throttle angle with focus on providing acceleration control, while at higher vehicle speeds, the pedal position is mapped to the electronic throttle angle with focus on controlling vehicle speeds.
However, the inventors herein have identified potential issues with such an approach. As an example, when the vehicle is travelling in regions of varying elevation, the pedal position map of Weber at al. may provide either too little torque or too much torque. For example, on an uphill grade, additional pedal movement may be required to provide the same speed, acceleration, or torque control, while ascending the grade Likewise, on a downhill grade, less pedal movement may be required to provide the same speed, acceleration, or torque control while descending the grade. As another example, even if the vehicle is not travelling on an uphill or downhill grade, the same issues may arise in the presence of headwinds or tailwinds. During all such operating conditions, the operator may need to be extra attentive and may need to frequently readjust the amount of pedal depression applied without knowing how much is necessary to maintain a desired vehicle speed (or vehicle acceleration). As such, this may degrade the drive feel and lead to operator dissatisfaction.
At least some of the above issues may be addressed by a method for controlling a vehicle engine comprising adjusting a relationship between an operator accelerator pedal depression amount and an engine output torque based on a grade of vehicle travel. In this way, by adjusting the relationship between pedal input and vehicle output using an indication of track elevation, the amount of driver effort required to maintain a level of vehicle performance may be reduced.
In one example, as the vehicle travels on an incline, the relationship between the pedal input and an engine output torque may be adapted with a higher gain based on the grade of uphill travel. This allows the vehicle to provide a higher output torque for a given pedal depression when climbing an uphill, and reduces the additional pedal movement required by the operator. As another example, when the vehicle travels on a decline, the relationship between the pedal input and an engine output torque may be adapted with a lower gain based on the grade of downhill travel. This allows the vehicle to provide a lower output torque for the given pedal depression when descending a downhill, and reduces the frequent pedal readjustment required by the operator. Similar adjustments may also be made in the presence of headwinds or tailwinds so that the driver's perception of vehicle performance is not degraded. Likewise, adjustments may be made to compensate for the effects of a load on the vehicle, such as when the vehicle is towing or carrying cargo or payloads, since a nominal relationship between the pedal input and the engine output torque may be based on an assumption of an unloaded vehicle.
Note that the relationship between driver pedal input and vehicle and/or engine output may be adjusted in a variety of ways, including gradually adjusting the relationship as environmental conditions change, as well as further adjusting the relationship based on various operating parameters such as engine speed, vehicle speed, gear ratio, etc. Further, gain adjustment may include adjusting software-based transfer functions, algorithms, analog circuitry, signal processing, and/or combinations thereof.
In this way, the amount of additional operator effort required to operate a vehicle while a road grade changes may be reduced. As such, this may improve the operator's perception of performance and the overall drive experience.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.